Potential Sources of Salts from Water-Rock Interaction

Potential Sources of Salts from Water-Rock Interaction during Hydraulic Fracturing:

An Experimental Study

Senior Thesis

Submitted in partial fulfillment of the requirements for the

Bachelor of Science Degree

At The Ohio State University

By

Michaela Wells

The Ohio State University

2015

Approved by

_______________________

Dr. David A. Cole, Advisor

School of Earth Sciences

TABLE OF CONTENTS

Abstract………………………………………………………………………..ii

Acknowledgements……………………………………………………………iii

1. Introduction…………………………………………………………………1

2. Methods

2.1 Sample Description and Analytical Techniques…………………….2

2.2 Sample preparation…………………………………………………3

2.3 X-Ray Diffraction………………………………………………….3

2.4 Sequential Leach Experiments……………………………………..4

2.5 Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDXS)…………………………………………………5

2.6 PHREEQC Geochemical Modeling……………………………….6

3. Results

3.1 X-ray diffraction of cuttings and core samples prior to sequential leaching………………………………………………………………..7

3.1.1 Cuttings samples…………………………………………8

3.1.2 Core Samples…………………………………………….11

3.2 Sequential Leach Experiments……………………………………..14

3.2.1 Calcium and magnesium…………………………………15

3.2.2. Sodium and potassium…………………………………..16

3.2.3 Strontium and barium……………………………………17

3.2.4 Sulfate and chloride………………………………………18

3.3 Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDXS) …………………………………………………20

3.4 PHREEQC Geochemical Modeling……………………………….. 26

4. Discussion……………….…………………………………….……………..27

5. Suggestions for Future Research……………………………………………….30

References Cited….……….……………………………………………………..33

Appendix A………………………………………………………………………34

Appendix B……………………………………………………………………….36

Appendix C………………………………………………………………………50

Appendix D………………………………………………………………………58

Appendix E……………………………………………………………………….62

ii

Abstract

Studying the composition and chemistry of post-hydraulic fracturing flowback waters is

important for understanding water-rock interaction in the subsurface and for how fluids injected

into a well during the fracturing process can affect flowback water chemistry. A recent issue has

risen involving the elevated concentrations of salts as total dissolved solids present in flowback

waters. Scientists have been investigating whether these salts are being dissolved from the formation

itself or if hydraulic fracturing fluids affect salt concentrations. This question was investigated by

performing sequential leach experiments to determine how cation and anion concentrations

dissolved into solution over time. Core and cuttings samples were obtained from southeastern Ohio.

Core samples are from the Point Pleasant Formation and cuttings samples are from the Utica

Formation. Various techniques were used to analyze samples including X-Ray diffraction (XRD) for

bulk mineralogy, scanning electron microscopy (SEM) for mineral-textural and elemental data, and

the use of PHREEQC Geochemical Modeling to determine saturation indices. The use of the SEM

allowed for the assessment of the amount of barite and other minerals present after sequential

leaching.

iii

Acknowledgements

I have so much gratitude in my heart for anyone and everyone who has been a part of

making my thesis a success as well as my college career. First and foremost, I would like to thank the

School of Earth Sciences at The Ohio State University for finding me when I was young and in

doubt and giving me a place to forever call my home not only academically but also for the

wonderful people in the department that has been a part of my journey.

I would like to give the biggest thanks to Dr. Dave Cole for taking me under his wing and

giving me the opportunity to be a part of the wonderful research group SEMCAL. I would like to

thank him for his abundant amount of knowledge in last year and a half. I am forever grateful to Dr.

Julie Sheets and Dr. Sue Welch for all of their time and effort put in to helping me prepare my

samples and analyze my data and always being there the moment I need help or for the many, many

emails and question that I have. Thank you both for your patience. Thanks goes to all of the

SEMCAL members and friends who have helped in any way contribute to the work I have

performed for this thesis.

I would like to thank all professors that have provided me with their knowledge in the

classes I have taken that have equally contributed to my overall understanding of the Earth Sciences:

Dr. Chin, Dr. Panero, Dr. Barton, Dr. Krissek, Dr. Olesik, Dr. Wilson, Dr. Cox, Dr. Judge, Dr.

Kelly, Dr. Darrah, Dr. Millan, Dr. Royce, Dr. Sawyer, Dr. Durand, Dr. Carey and Dale Gnidovec. I

wish to thank all of the graduate and undergraduate TA’s for all labs and classes for all of the time

and effort put in to my understanding in those classes. A big thanks to Dr. Royce for keeping me

straight and figuring out the many problems that I seem to have as wells as all of the questions.

Thank you for the patience!

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A big thanks to any lab partners I have had in the major: Scott Hull, my Mineralogy and

Petrology buddy always making working on labs fun and enduring. Same goes for my Apartment 9

roommates and friends at field camp: John Jones, Brendon Mock and Megan Mave. Thanks for all

of the wonderful memories that will last a lifetime.

Thank you to my family. I would like to thank my mom, dad and sister for ALWAYS having

faith in me even though there were times when we all weren’t sure if I would make it this far. There

aren’t words to describe my love for my family and how that love gets me through every day. My

grandparents on both sides who have always had faith in me, encouraged me and have prayed for

me to accomplish all of my goals and watch me do great things. My aunts, uncles and cousins who

have always kept interest in my personal and academic goals and have always been there for me even

in distance. Thank you to my friends. Taylor Allen: This peach has been by my side since day 1

when I lost my BuckID in the stairwell of Houck House. We started in Chemical Engineering

together and she was the reason I had found Earth Sciences. We switched to Earth Sciences

together and she supports me in everything I do. She is always that bit of excitement and craziness

that I need every day and in ES classes together with crazy jokes only we get and teachers who just

don’t understand. Bridgette Kelly: Now this girl has really been by my side since before day 1. We

met on Facebook before Freshman year and she was my roommate. She is the sweetest, most

loving, crazy girl I know and always has a way to cheer me up and to push on through all troubles.

Maddie Duncan: This girl has been by my side since Freshman year. She is always there for me, gives

words of support and wisdom and always cheers me up even in the worst of times. I would also like

to thank all of the friends I have made in the School of Earth Sciences and I can honestly call all of

them my family. Lastly, a big thanks to The Lord for always and forever being there, watching over

me and guiding me in all endeavors and giving me the strength to always be the best person I can be.

There are many other things I could say, but words can’t do justice for how the heart feels...

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1. Introduction

A growing concern has been identified involving the presence of salts as total dissolved

solids in post-hydraulic fracturing flowback waters. Scientists have been investigating the

characteristics of these dissolved solids from different gas shale systems to develop protocols to

properly dispose of the flowback fluid under regulatory conditions. The quality of the flowback

water can be dependent on many factors such as the chemistry associated with hydraulic fracturing

fluids in contact with the formation, fluids in contact with formation water, the formation itself and

the amount of time the fluid was retained in the well and the initial quality of the fluid used in the

process (Vazquez et al. 2014).

The flowback water returns to the surface when pressure is released on the well. The

majority of flowback returns within the first few days or weeks, while the remainder returns slowly

over time as hydrocarbons are produced. During the first few days, the level of total dissolved solids

rises very quickly with concentrations around 100 to 300 grams/liter after approximately 7-30 days

(Stewart et al. 2015). The origin of dissolved solids, including the mixing with subsurface

groundwater and dissolution of evaporates is still being studied (Stewart et al. 2015). When water-

rock interactions take place, metals, salt ions and organic compounds can be released (Wilke, 2015).

This experimental study examines the extent to which water-soluble salts are released during

water-rock interactions in sequential leach experiments. The purpose of this work is to investigate

the mineralogical and chemical composition of core and cutting samples, and to conduct benchtop

water-rock interaction experiments to determine the sources of dissolved solids in the flowback

waters produced during hydraulic fracturing. The objective is to determine whether these dissolved

constituents originate from the formation itself, the drilling muds or from hydraulic fracturing fluid

used in the fracturing process?

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2. Methods

2.1 Sample Description and Analytical Techniques

Several methods were used to prepare and analyze the cuttings and core samples of gas shale

obtained from southeastern Ohio for this experiment. Two core samples were chosen because they

were from the zone of interest for hydraulic fracturing and three cuttings samples were chosen to try

and match core depths. However, it was later determined that core samples were from the Point

Pleasant Formation and cuttings samples were from the overlying Utica Formation. Sample numbers

are subsamples of the two core and three cuttings samples used in this experiment. Cuttings depths

represent total distance within the hole, with some vertical component and some lateral component.

Operators describe the depth to the turn (toward the lateral) as being around 7000 feet. Core and

cuttings samples used in this experiment along with their corresponding depths, formations and

leachates used are shown in Table 1 below:

Table 1: Samples and their corresponding depths, formations, leachates and type

The supply of cuttings samples available from depths 8470 ft–8500 ft and 8530 ft–8560 ft was

sufficient only to perform the sequential leach experiments. Cuttings from depth 8500 ft–8530 ft

were used for mineralogical assessment via XRD and were not the same material used in the leach

experiment. However, all cuttings came from the same formation, the Utica. As will be shown

Sample Number Depth (ft) Formation Leachate Used Type

M1 8549 ft Point Pleasant Water Core

M2 8549 ft Point Pleasant Acid Core



M5 8470 ft-8500 ft Utica Water Cuttings



M8 8470 ft-8500 ft Utica Acid Cuttings



3

below, a comparison of results from experiments using the core and cuttings does allow for a

comparison between a clay-rich shale (the Utica) and a carbonate-rich shale (the Pt. Pleasant).

2.2 Sample preparation

Samples were first observed for physical characteristics, such as color and texture to note any

differences related to sample depths. Then, approximately 1 gram of each sample was hand ground

using a mortar and pestle. Gloves were worn during this process to avoid introducing

contamination. Core samples were ground to approximately the same grain size (approximately silt

to coarse clay sized) as cutting samples to avoid grain size bias. Mortar and pestle were thoroughly

cleaned between each grinding session to avoid cross-contamination between samples.

2.3 X-Ray Diffraction

Core and cuttings samples were then prepared for XRD analysis to determine bulk

mineralogical composition. A table of samples analyzed for XRD is presented in Table 2. All

samples were loaded into a specified magazine slot and analyzed with a PANalytical X’Pert Pro X-

ray diffractometer at the Subsurface Energy Materials Characterization and Analysis Laboratory

(SEMCAL), School of Earth Sciences, The Ohio State University. This instrument is equipped with

a high speed X’Celerator detector. Data were collected from 4 to 70 degrees 2-theta with a voltage

of 45 keV and tube current of 40 mA (CuKα radiation). Sample scans were viewed and compared

using PANalytical DataViewer software. The scans were then opened in PAnalytical HighScore Plus

to be analyzed for bulk mineralogy. Data for all samples were corrected for background by applying

a granularity of 19 and a bending factor of 0. Peak search was run using a minimum significance of

1.00, a minimum tip width of 0.10, a maximum tip width of 1.00 and a peak base width of 2.00. The

method applied used a minimum 2nd derivative. Scans were analyzed with the pattern matching

algorithm in HighScore Plus, using the PDF 4+ mineral database. Minerals relevant to the samples

4

were accepted as candidates and non-relevant minerals were rejected. Each candidate accepted was

analyzed for pattern lines to ensure that the highest intensity lines were matched, leading to

confidence in the mineral selected.

Table 2: XRD samples and their corresponding depths, formations and type

2.4 Sequential Leach Experiments

In order to determine the readily soluble salt content of the solid phase, samples of the core

and cuttings powders were subjected to a series of sequential leach experiments at room temperature

and ambient pressure. Temperature and pressure conditions typical in the complex subsurface were

not replicated in order to keep temperature and pressure a constant for this experiment. It is

assumed that room temperature did not fluctuate more than a few degrees during the course of this

experiment. Each sample was divided into two subsamples, weighing approximately 0.5g, and placed

into a 50mL Falcon tube. All samples were weighed on a Mettler Toledo pan balance. Subsample

weights are listed in Table 3A in Appendix A. One set of subsamples (M1, M3, M5, M6, M7) was

leached in 50mL of distilled Mili-Q water. The second set of subsamples M2, M4, M8, M9 and M10

was reacted in 50 ml Mili-Q water with 0.5mL of 0.1M HCl (~ 1 mM HCl). As will be seen in the

results, too much acid was inadvertently added to all samples for the fourth leach either by setting

the automatic pipette incorrectly or by using the wrong bottle of acid. All samples were thoroughly

mixed at the start of the experiment. Two experimental blanks were prepared using the same

5

distilled Milli-Q water plus acid to determine if salts or trace metals were present in the water, acid,

or leached from the Falcon tubes.

All solid phase samples were leached sequentially 4 times, following the same fluid addition

procedures for each set-up. The supernatant fluid was removed with a transfer pipette and solutions

were filtered with a 0.45 micron pore size syringe filter. Not all of the supernatant fluid was removed

during this process to avoid disturbing the powdered rock sample in order to keep the water-rock

ratio fairly consistent. The time for each leach experiment was increased for subsequent leaches to

simulate increased water-rock interaction time in the subsurface. Leach 1 was allowed to sit for 1 day

and then fluid was removed. Leach 2 lasted 2 days, leach 3 lasted two weeks, and leach 4 was

sampled after three weeks. After Leach 1, the Falcon tubes were reweighed before continuing to the

set-up of Leach 2, to ensure minimal solid phase sample loss during the removal of fluid, and also to

ensure that the fluid-rock ratio would still be approximately the same. After the supernatant fluid

was removed from Leach 4, the solid phase samples were allowed to air dry before analysis using the

SEM. Fluid samples were analyzed for select major and trace elements using an Inductively Coupled

Plasma Optical Emission Spectrometer (ICP-OES). Anion concentrations were measured using a

Dionex Ion Chromatograph using the methods of Welch et al. (1996).

2.5 Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDXS)

The core and cuttings samples from the final leach experiment were prepared for analysis

with the FEI Quanta 250 Field Emission SEM. A small fraction of the reacted powder was adhered

to an aluminum stub with carbon tape. Loose material was tapped off the stubs before coating with

Au/Pd with a Denton Desk V precious metal sputter coater to prevent charging.

Images were acquired using a backscattered electrons BSE detector and a secondary electron

detector (Everhart-Thornley). Images were acquired using an accelerating voltage of 15keV, a

6

working distance of ~13 mm and a spot size of 4.0. Spot analyses were taken of regions of interest

using a Bruker Xflash Energy Dispersive X-Ray Spectrometer. The energies of characteristic X-rays

were used to determine the elemental compositions of minerals subjected to the spot analysis.

2.6 PHREEQC Geochemical Modeling

Geochemical modeling was used to determine saturation indices of selected phases using

PHREEQC version 3.1.7-9213. This version can be downloaded from the United States Geological

Survey website: http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/ . Solution alkalinity

was estimated for each sample from the charge balance between measured anions and cations.

http://wwwbrr.cr.usgs.gov/projects/GWC_coupled/phreeqc/

7

3. Results

3.1 X-ray diffraction of cuttings and core samples prior to sequential leaching

XRD analysis was used to determine bulk mineralogy of the core and cuttings samples used

in the leach experiments. Understanding the initial mineral composition is necessary for assessing

sample textures and mineralogy after the leach experiments. Core and cuttings samples analyzed on

XRD along with their corresponding depths and formations are shown in Table 2.

It must be kept in mind that core and cuttings samples represent rock from different depths,

and more importantly different formations. This difference is reflected in the XRD data (Figure 1).

Core samples represent a true vertical depth, while cuttings samples represent a total depth from the

borehole which includes vertical as well as lateral depth when drilling took a turn in the process.

XRD individual raw data scans are in presented in Appendix A. Based on log data and the XRD

results, the core samples represent rock material from the Point Pleasant, while cuttings represent

material from the Utica.

Figure 1: Combined core and cuttings raw data. Purple corresponds to core from depth 8479 ft

(predominantly fine-grained matrix) in the Point Pleasant Formation, pink -core from depth 8479

ft (predominantly carbonate), brown- core from depth 8549ft (carbonate and matrix). Blue

corresponds to cuttings from depth 8410 ft-8440 ft from the Utica Formation, red- cuttings from

depth 8500 ft-8530 ft, green- cuttings from depth 8680 ft-8710 ft.

8

3.1.1 Cuttings samples

The XRD scan for cuttings sample at a depth of 8410 ft–8440 ft shows a clay-rich

mineralogy (Figure 2). This scan includes results of the peak matching routine in the HighScore Plus

analytical platform. Illite/muscovite are identified based on the 10-angstrom d-spacing peak at 9.01

degrees 2-theta. Calcite and dolomite are identified based on the 100 relative intensity lines at 29.43

and 30.98 degrees 2-theta, respectively, as well as the presence of most expected peaks over the

entire 2-theta range of the scan (5-70 degrees 2-theta). Pyrite is evident based on the 1.63-angstrom

d-spacing peak at 56.34 degrees 2-theta. The highest intensity (major) peak for albite is identified at

28.0 degrees 2-theta (d-spacing 3.19 angstroms). The 14-angstrom (001) peak for chlorite (pattern

matched to clinochlore) is also present, as is its corresponding 7-angstrom (002) peak around areas

of 4.0 and 12.0 degrees 2-theta. Strontianite is identified based on the peak at 25.86 degrees 2-theta

(the 100 relative intensity line), but its identification is tenuous based on peak overlap with

clinochlore. The 100 relative intensity line for barite (not shown) can be identified based on a 3.45-

angstrom d-spacing (25.86 degrees 2-theta) that may overlap with strontianite.

9

Figure 2: XRD scan for cuttings depth 8410 ft–8440 ft (one-quarter divergence slit), showing minerals identified

The cuttings sample from depth 8500 ft–8530 ft also has a clay-dominated mineralogy

(Figure 3). Much like cuttings depth 8410 ft–8440 ft, illite, muscovite, and chlorite compose the

phyllosilicates. Other major minerals include calcite, dolomite, and quartz, with minor pyrite and

albite. Strontianite is tentatively identified based on its major peak at the 25.86 degrees 2-theta

position but again, this overlaps with clinochlore.

10

Figure 3: XRD scan for cuttings depth 8500 ft–8530 ft (20s count time; one-quarter divergence slit)

The cuttings sample from depth 8680 ft–8710 ft has a clay dominated mineralogy much like

the previous cuttings depths shown (Figure 4). Calcite, dolomite and quartz with minor amounts of

pyrite and albite are present. As with the sample from depth 8500–8530 ft, strontianite is defined by

its high intensity peak at around 25.86 degrees 2-theta but this shows overlap with clinochlore.

11

Figure 4: XRD scan for cuttings depth 8680 ft–8710 ft (one-quarter divergence slit)

3.1.2 Core Samples

The XRD scan for core depth 8549 ft shows a carbonate-rich mineralogy compared to the

cuttings samples (Figure 5). Illite/muscovite are identified based on the 10-angstrom d-spacing peak

at 9.01 degrees 2-theta. Calcite and dolomite are identified based on the 100 relative intensity lines at

29.43 and 30.98 degrees 2-theta, respectively, as well as the presence of most expected peaks over

the entire 2-theta range of the scan. Calcite shows the highest peak intensity (counts) in core

samples, as compared to cuttings samples where quartz is the highest intensity peak. Quartz is

identified based on its 100 relative intensity line at 26.67 degrees 2-theta. Pyrite is evident based on

the 1.63-angstrom d-spacing peak at 56.34 degrees 2-theta. The highest relative intensity (major)

peak for albite is identified at 28.0 degrees 2-theta (d-spacing 3.19 angstroms), respectively. A 7-

angstrom peak for amesite at 12.0 degrees 2-theta is also present.

12

Figure(5): XRD scan for core (matrix and carbonate) depth 8549 ft

The XRD scan for core depth 8479 ft (carbonate) again shows a carbonate-rich mineralogy

as compared to the cuttings samples (Figure 6). Muscovite is identified based on the 10-angstrom d-

spacing peak at 9.01 degrees 2-theta. Calcite is again identified based on the 100 relative intensity line

at 29.43 degrees 2-theta, and the occurrence of most expected peaks over the entire 2-theta range of

the scan. Calcite shows strong overlap with magnesium calcite and chalcopyrite around 29.43

degrees 2-theta. Quartz is identified based on its 100 relative intensity line at 26.67 degrees 2-theta.

Pyrite is evident based on the 1.63-angstrom d-spacing peak at 56.34 degrees 2-theta and its 2.71-

angstrom d-spacing peak (85 relative intensity line) at 33.07 degrees 2-theta. The highest intensity

(major) peak for ankerite (Ca(Fe,Mg,Mn)(CO3)2) is identified at 31.0 degrees 2-theta (d-spacing 2.91

angstroms).

13

Figure 6: XRD scan for core (predominantly carbonate) depth 8479 ft

The XRD scan for core depth 8479 ft (matrix), shows a carbonate dominated mineralogy,

similar to the previous core samples (Figure 7). Illite/muscovite and calcite and dolomite are once

again identified at the respective 2-theta positions as in the first core scan. Quartz and pyrite again

are present at the same 2-theta positions as in previous core scans. The highest intensity (major)

peak for albite is identified at 28.0 degrees 2-theta, d-spacing 3.19 angstroms, respectively. A 12-

angstrom peak for chamosite is also present. The scan for the clay-rich matix is given in Figure 7).

14

Figure 7: XRD scan for core (predominately fine-grained matrix) depth 8479 ft

3.2 Sequential Leach Experiments

For the water-rock experiments, three cuttings samples from the Utica Formation and two

core samples from the Point Pleasant Formation were sequentially leached in water and dilute acid

to determine the possible source of dissolved salts in flowback fluids. The results of these

experiments show in general that the total solute release from the solid phase was greater in dilute

acid than in water. The cuttings samples experiments in general had much higher solute

concentrations than core using both water and acid leachates. Below is a summary of the results

grouped by common element associations.

15

3.2.1 Calcium and magnesium

As seen in Figure 8a, the use of an acid as a leachate greatly affected the amount of calcium leached

into solution. The source of calcium most likely is coming from calcium carbonate in both core and

cuttings samples. The dissolution of calcite in acid can be written as follows:

𝐶𝑎𝐶𝑂3 + 2𝐻+ ↔ 𝐶𝑎2+ + 𝐶𝑂2 + 𝐻2𝑂 (1)

It became evident that too much acid was added during the set-up process for the fourth

leach as there is a greater amount of calcium leached out compared to all other leaches. Perhaps the

most important result from examining calcium concentrations is the affect that calcium carbonate

had on the relative pH of acid samples. After the first and second leaches that were allowed to sit for

1 and 2 days, the pH of the acid leachates went from around a pH of 3 to a neutral pH. The

buffering of the solution by calcite dissolution could explain this pH dependency. This is shown in

Figure 8b.

As seen in Figure 8c, the use of an acid leachate affected the amount of magnesium leached

out of solution but not to the same extent of calcium as seen above. The concentration of

magnesium in solution depends on the initial solution pH, as magnesium in solution in the leach

experiments is typically 2–3 times higher in the acid leach compared to the water leach experiments.

However, this is much less than what was observed for calcium. In core samples, the magnesium

concentration was higher in the acid leach compared to the water leach but the magnesium

concentrations in subsequent leaches increased for all samples because the water-rock interaction

time increased. In cuttings samples, the concentration of magnesium was again higher in acid

samples as compared to water. The concentration stayed relatively the same after the first two

leaches and then spiked after the third leach (2 weeks). These increases in concentrations over time

16

are most likely due to the dissolution of Mg-bearing calcite and/or dolomite. The dissolution of

dolomite in acid can be written as follows:

𝐶𝑎𝑀𝑔(𝐶𝑂3)2 + 4𝐻+ → 𝐶𝑎2+ + 𝑀𝑔2+ + 2𝐶𝑂2 + 2𝐻2𝑂 (2)

Dissolution of other magnesium-bearing minerals identified in the XRD data, such as chlorite, could

have contributed to the rapid increase after the third leach. Samples that used an acid leachate

showed more magnesium after the fourth leach like with calcium above due to accidental addition of

too much acid during the set-up process.

3.2.2. Sodium and potassium

A large amount of sodium was leached out of both core and cuttings after the first leach

(Figure 9a). In core samples, there was little to no sodium being dissolved after the second leach.

Only a small amount of sodium dissolved in cuttings samples after the second and third leaches.

Figure 8a: Calcium concentrations M1-M10 Leaches 1-4

Figure 8b: Post-leach pH values

Figure 8c: Magnesium concentrations M1-M10 Leaches 1-4

17

There was almost five times more sodium dissolved out of cuttings samples as compared to core.

The decrease in concentrations in water from cuttings samples after the first leach compared to the

increase in concentrations in acid cuttings samples could be a result of a mineralogical difference

between the subsamples.

A large amount of potassium was leached out of both core and cuttings samples using both

acid and water as a leachate (Figure 9b). In cuttings samples, there was a large amount of potassium

that dissolved after the first leach. In core samples, an acid leachate leached out more potassium

initially and then all sample concentrations slowly decreased for subsequent leaches, most likely

because the reactive potassium phase present in the clays became depleted over time .In cuttings

samples, potassium concentrations were lower after the first leach. The source of potassium in

cuttings is most likely from drilling fluid used during hydraulic fracturing whereas the source of

potassium in core is most likely from the illite/muscovite reactive clay phases present in the rock.

3.2.3 Strontium and barium

One of the most striking observations about the strontium concentrations is that they seem

to be very similar to magnesium concentrations (Figure 10a). Reaction time seems to increase

concentrations in core samples but deplete concentrations in cuttings samples. Perhaps cuttings

Figure 9a: Sodium concentrations M1-M10 Leaches 1-4

Figure 9b: Potassium concentrations M1-M10 Leaches 1-4

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samples contained strontium that was not readily soluble due to a mineralogical difference. The

leaching of strontium into solution is believed to follow calcium and magnesium because it is

released during the dissolution of calcite and dolomite where it occurs as a minor constituent.

The barium concentrations were significantly higher in all cuttings samples as compared to

core samples Figure(10b). However, barium dissolution from core samples is readily detected and

shows trends that can be explained by increase in reaction time. Barium concentrations are not

significantly higher in either the core or cuttings samples leached in acid and water.

3.2.4 Sulfate and chloride

A correlation is observed between the use of acid as a leachate and the lowering of the

sulfate concentrations as compared to water samples (Figure 11a). Cuttings samples leached sulfate

into solution by a factor of 1.5 times more than core. Over time, sulfate concentrations decreased in

all samples until the third leach when concentrations seem to rise again. When comparing barium

and sulfate relative to each other, it appears as if sulfate concentrations are lowered minimally by

using an acid leachate but the use of acid actually increases the barium concentrations in the same

samples. This trend occurs in both core and cuttings, but occurring a small amount more in cuttings.

This suggests that there may be a reaction occurring between barium and sulfate.

Figure(10a): Strontium concentrations M1-M10 Leaches 1-4

Figure(10b): Barium concentrations M1-M10 Leaches 1-4

19

The use of a hydrochloric acid leachate affected the amount of chloride present in both core

and cuttings samples (Figure 11b). The amount of Chloride leached is not pH dependent. Chloride

not only was leached out of the samples themselves but also more was present in all samples from

the fourth leach which was due to accidentally adding too much acid as a result of either accidentally

setting the automatic pipette wrong or using the wrong concentration of acid. The slow increase in

chloride in acid leaches in both core and cuttings is a result of not entirely removing the supernatant

solution for each leach in an attempt to preserve water-rock ratios. It is possible that the slow

increase in chloride also is coming from the minerals in the samples that contain chloride in their

bulk mineralogy.

Figure 12a below shows the effect of using an acid as a leachate on core and cuttings samples when

analyzing barium versus sulfate. Leaches 1, 2 and 4 are presented in Figures(1C), (2C) and (4C) in

Appendix C. The same can be seen in figures (12b) and (12c) showing barium + strontium versus

sulfate. This again shows the effect of using an acid as a leachate on core and cuttings samples.

Leaches 1 and 4 are presented in Figures (5C) and (8C) in Appendix C.

Figure 11a: Sulfate concentrations M1-M10 Leaches 1-4

Figure 11b: Chloride concentrations M1-M10

Leaches 1-4

20

3.3 Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDXS)

Dried samples used in the sequential leach experiments were analyzed on the SEM to

identify changes in the physical and chemical characteristics. Analysis was done to acquire mineral

textural data and then specific grains were targeted using EDXS to acquire elemental data. The

most surprising result was that there was still abundant barite in the cuttings samples, even after the

fourth leach that had been allowed to react for three weeks. However, there was little to no barite

detected in the in core samples. Figures 13 and 14 show significant amounts of barite present in

sample M8, a cuttings sample leached in acid, as evident from the bright minerals in the BSED

image. The elemental signatures were confirmed by using EDXS shown in Figure 15.

Figure 12a: Barium vs. Sulfate concentrations

Leach 3 Figure 12b: Strontium + Barium vs. Sulfate concentrations Leach 2

Figure 12c: Strontium + Barium vs. Sulfate concentrations Leach 3

21

Figure 13: Cuttings sample leached in acid from depth 8470 ft-

8500 ft in the Utica Formation showing a presence of barite

represented by the bright grains in the BSED image.

Figure 14: Cuttings sample leached in acid from depth 8470 ft-

8500 ft in the Utica Formation showing a large, euhedral

barite grain with smaller grains throughout the BSED image.

22

The results proved the same when analyzing cuttings samples leached in only water as seen in

Figures 16 and 17 below. Chemistry was confirmed using EDXS shown in Figure 18 below.

Figure 15: EDXS data showing chemistry of cuttings sample leached in acid from depth 8470 ft-

8500 ft in the Utica Formation where spot analysis was taken on the large, euhedral grain

presented in the BSED image.

Figure 16: Cuttings sample leached in water from depth 8470

ft-8500 ft in the Utica Formation showing barite grains

throughout the BSED image.

23

Figure 17: Cuttings sample leached in water from depth 8500

ft-8530 ft in the Utica Formation showing a large, euhedral

barite grain with smaller grains throughout the BSED image.

Figure 18: EDXS data showing chemistry of cuttings sample leached in water from depth 8500

ft-8530 ft in the Utica Formation where spot analysis was taken on the large, euhedral grain


24

SEM analysis was also performed on core samples. Core samples, like the one presented in Figure

19, exhibited dissolution textures which can be tied to the mineralogy of the sample. The mineralogy

was confirmed using EDXS spot analysis (Figure 20).

Figure 20: EDXS data showing calcium carbonate chemistry of core sample leached in acid

from depth 8479 ft in the Point Pleasant Formation where spot analysis was taken on the

dissolution surface presented in the BSED image.

Figure 19: Core sample leached in acid from depth 8479 ft in

the Point Pleasant Formation showing dissolution textures

throughout the BSED image.

25

Pyrite framboids were evident when scanning over the samples and were easy to identify.

This result confirms the XRD data for core samples that indicated the presence of significant

amounts of pyrite. Its image and corresponding EDXS spot analysis are presented in Figures 21 and

22.

Figure 21: Acid-leached core sample from depth 8549 ft in the

Point Pleasant Formation showing pyrite framboids

surrounded by illitic clay throughout the BSED image.

26

3.4 PHREEQC Geochemical Modeling

The use of PHREEQC geochemical modeling software allowed for the analysis of saturation

indices for relevant minerals in this experiment. Initial inputs are represented in Tables 1E-4E in

Appendix E. All phase saturations for samples and leaches are presented in Tables 5E-44E in

Appendix E. Mineral saturations were analyzed for phases aragonite, calcite, dolomite, barite,

celestite, gypsum and strontianite. The use of a dilute acid leachate effectively brought the phases

closer to saturation than by using only water. The most important observation made from this

modeling procedure was that barite proved to be near perfect saturation in all cuttings samples after

the fourth leach.

Figure 22: EDXS data confirming pyrite presence in core sample leached in acid from depth

8549 ft in the Point Pleasant Formation where spot analysis was taken on the bright framboids


27

4. Discussion

As stated previously, cuttings samples had been chosen as a means of correlation to core

samples from the pay zone. It was discovered later on that cuttings samples and core samples were

indeed from two different formations. This provided a new opportunity to compare and contrast

organic-bearing shales that differ in bulk mineralogy such as in this experiment; the clay-rich Utica

Formation vs. the carbonate-rich Point Pleasant Formation.

Results from Utica Formation cuttings samples analyzed showed a clay-rich consistency

evident initially in XRD results. Clay-rich phyllosilicate minerals such as illite, muscovite and chlorite

dominate bulk mineralogy. Cuttings samples leached large amounts of calcium, magnesium, sodium,

potassium, barium, strontium and sulfate and chlorine. Acid used as a leachate proved to leach these

readily soluble minerals into solution more than using only water, although a fair amount still

leached into solution with water and almost all samples leached more than core samples with the

exception of magnesium, calcium, chlorine and strontium. Acid affected the carbonates in a way that

caused fast dissolution of calcite and dolomite. This rapidly effected pH, as the acid leachate with an

initial pH of 3 started neutralizing to a pH of around a 7. This change occurred within approximately

one day. Fast neutralization of pH from carbonate dissolution consequently effected pH

dependency of proceeding minerals leached into solution to having almost no dependence.

However, calcium and magnesium both show strong pH dependence as is evident in the results.

Cuttings samples showed a large presence of barite in SEM images that was not evident in core

samples although that does not rule out its presence core samples.

Results from Point Pleasant Formation core samples analyzed showed a carbonate rich

consistency as indicated in the XRD results where the calcite and dolomite dominate bulk

mineralogy with some minor clays and pyrite. Core samples leached reasonable amounts of calcium,

28

magnesium, sodium, potassium, barium, strontium, sulfate and chlorine. Acid equally affected

carbonate dissolution in core samples as in cuttings samples. SEM analysis showed evidence of

dissolution pits in areas proven to be calcite in core acid samples. Core and cuttings samples proved

to be leaching salts such as calcium chloride, sodium chloride and potassium chloride. A recent

study by Blauch et. al (2009) on the Marcellus shale states that post-fracking flowback waters are

characterized by sodium chloride and calcium chloride waters from brine deposits formed from

evaporated seawater within the formation due to fluid mobilization into it. It is also stated that

dolomitization occurs from water-rock interactions from diagenetic processes. One can argue that

calcite and dolomite from samples in this thesis experiment originate from the Utica and Point

Pleasant Formations themselves as their dissolution rates seem to be relatively the same in core and

cuttings samples. A hypothesis for the source of additional magnesium in cuttings samples is that it

may have originated from chlorite that is omnipresent in cuttings samples as seen in XRD results.

Calcium chloride and sodium chloride also could be originating from natural formation salts.

Interestingly, Blauch et al. (2009) also found that barite, calcite, and dolomite were all saturated with

respect to themselves. The use of PHREEQC in this thesis experiment showed similar results

however, barite did not become saturated until it was leached out of cuttings samples. Calcite,

dolomite and celestite remain under saturated with respect to themselves. Because of the striking

difference in barite concentrations between core samples and cuttings samples, it is hypothesized

that the majority of barite was introduced during the fracturing process. This hypothesis holds the

same for the presence of potassium only it cannot be ruled out that potassium in core samples is

from the minor illite/muscovite clay phases present in the formation. The source of strontium can

be hypothesized to be coming from the formation itself because it is known to follow calcium and

magnesium. It can be concluded that an acid leachate was the most influential variable on the release

29

of carbonates and sodium, calcium and potassium chlorides and time were the most influential

variables for the release or depletion of all other minerals such as barium, strontium and sulfate.

30

5. Suggestions for Future Research

Presently, sequential leach experiments are being performed on a new set of samples. All

samples being used are from the same core and cutting depths as the core and cutting samples used

for this thesis experiment. Unfortunately, the set-up and analysis of these experiments could not be

finished before this thesis was published. Description of the work already performed on the samples

and the future steps to be included in the experiments are described below. Additional suggestions

for future work will also be discussed.

Samples and their corresponding depths are represented in Table 3:

Table 3: Samples used and their corresponding depths

The sample weights for this experiment are different, however, from the weights used in the

sequential leaches for this thesis experiment. Weights of samples are represented in Table 4:

Table 4: Pre- hard leach sample weights

Sample Numbers Sample Depths (ft)

M1 and M2 8549

M3 and M4 8479

M5 and M8 8470 ft-8500 ft

M6 and M9 8500 ft-8530 ft

M7 and M10 8530 ft-8560 ft

Depths of Samples

Sample Number Weight (g)

M1 0.533 g

M2 0.528 g

M3 0.584 g

M4 0.593 g

M5 0.508 g

M6 0.518 g

M7 0.526 g

M8 0.508 g

M9 0.509 g

M10 0.576 g

Weights of Samples Pre-Leach

31

Preparation of samples followed the same set-up procedures as the samples used in this thesis

experiment. The experiment in progress follows the procedures of a similar experiment performed

by Stewart et al. (2015) in which fluids injected during hydraulic fracturing are replicated in a lab.

For this experiment, the samples undergoing water leaching had been set up months prior

and were allowed to sit for 5 months, 17 days. Samples M2, M4, M8, M9 and M10 were not used for

this experiment as they contain acid with the same water-acid ratio used in this thesis experiment

and would not follow the procedures described by the Stewart et al. (2015). Acid samples were set

aside and left to dry after fluid to be analyzed was removed and will be prepped for future SEM

analysis. Fluid from water samples M1, M3, M5, M6 and M7 was removed to be analyzed in the

future and a new leachate was prepared following the second step in the journal being replicated.

The purpose of the water leach in step 1 was to extract soluble salts and evaporated pore water. Step

2 was then set up by preparing ammonium acetate with a pH of 8. pH of ammonium acetate was

tested and corrected to acquire a value close to a pH of 8. Initial pH value obtained was 7.13 and a

dropper of ammonium hydroxide was added and pH was tested again with a new acquired value of

7.8. Approximately 50 mL of the ammonium acetate solution was added to the samples. Samples

were shaken approximately 50 times to ensure rock and water were thoroughly mixed. This second

step leach was then allowed to sit for 3 days. Fluid was then removed to be analyzed in the future.

All fluids were removed following the same process used for this thesis experiment. The purpose of

the ammonium acetate leach in step 2 was to extract surface exchangeable and low-charge

interlayers.

Future leachates to be added and removed from the samples for future analysis include 8%

acetic acid with a purpose to extract carbonate minerals, 0.1M HCl with a purpose to extract high-

32

charge interlayers and partial silicate/oxides and a total dissolution using HF, HNO3 and HClO4

with a purpose to extract silicates and remaining refractory minerals.

33

References Cited

Blauch, M. E., Meyers, R. R., Moore, T. R., Lipinski, B. A., & Houston, N. A. (2009). Marcellus

Shale Post-Frac Flowback Waters – Where is All the Salt Coming From and What are the

Implications? Society of Petroleum Engineers.

Stewart, B. W., Chapman, E. C., Capo, R. C., Johnson, J. D., Graney, J. R., Kirby, C. S., et al. (2015).

Origin of brines, salts and carbonate from shales of the Marcellus Formation: Evidence from

geochemical and Sr isotope study of sequentially extracted fluids. Applied Geochemistry, 60, 78-

88.

Vazquez, O., Mehta, R., Mackay, E., Linares-Samaniego, S., Jordan, M., & Fidoe, J. (2014). Post-frac

Flowback Water Chemistry Matching in a Shale Development. Society of Petroleum Engineers.

Welch, K. A., Lyons, W. B., Graham, E., Neumann, K., Thomas, J. M., & Mikesell, D. (1996).

Determination of major element chemistry interrestrial waters from Antarctica by ion

chromatography. Journal of Chromatography A, 739, 257–263.

Wilke, F. D. H., Vieth-Hillebrand, A., Naumann, R., Erzinger, J., & Horsfield, B. (2015). Induced

mobility of inorganic and organic solutes from black shales using water extraction:

Implications for shale gas exploitation. Applied Geochemistry, 63, 158-168.

34

Appendix A

Sample Description Tables

Table 1A: Samples and their corresponding depths, formations, leachates and type

Table 2A: XRD samples and their corresponding depths, formations and type

Table 3A: Pre-leach sample weights

Sample Number Depth (ft) Formation Leachate Used Type












M1 0.541 g

M2 0.521 g

M3 0.551 g

M4 0.412 g

M5 0.577 g

M6 0.554 g

M7 0.477 g

M8 0.421 g

M9 0.468 g

M10 0.567 g


35

Table 4A: Pre- hard leach sample weights

Figure 1A: Post-leach pH values


M1 0.533 g

M2 0.528 g

M3 0.584 g

M4 0.593 g

M5 0.508 g

M6 0.518 g

M7 0.526 g

M8 0.508 g

M9 0.509 g

M10 0.576 g


36

Appendix B

XRD Results

Figure 1B: Cuttings 8410 ft-8440 ft quarter divergence raw data

37

Figure 2B: Cuttings 8500 ft-8530 ft 20s quarter divergence raw data

38

Figure 3B: Cuttings 8680 ft-8710 ft quarter divergence raw data

39

Figure 4B: Combined cuttings quarter divergence raw data

40

Figure 5B: Core (carbonate) 8479 ft raw data

41

Figure 6B: Core (matrix) 8479 ft raw data

42

Figure 7B: Core (matrix and carbonate) 8549 ft raw data

43

Figure 8B: Combined core and cuttings raw data

44

Figure 9B: XRD scan for cuttings depth 8410 ft-8440 ft (one-quarter divergence slit), showing minerals

identified

45

Figure 10B: XRD scan for cuttings depth 8500 ft-8530 ft (20s count time; one-quarter divergence slit)

46

Figure 11B: XRD scan for cuttings depth 8680 ft- 8710 ft (one-quarter divergence slit)

47

Figure 12B: Core (predominantly carbonate) depth 8479 ft

48

Figure 13B: Core (predominately fine-grained matrix) depth 8479 ft

49

Figure 14B: Core (matrix and carbonate) depth 8549 ft

50

Appendix C

Sequential Leach Experiments

Figure 1C: Barium vs. Sulfate concentrations Leach 1


51



52

Figure 5C: Strontium + Barium vs. Sulfate concentrations Leach 1


53



54

Figure 9C: Barium concentrations M1-M10 Leaches 1-4

Figure 10C: Strontium concentrations M1-M10 Leaches 1-4

55

Figure 11C: Sulfate concentrations M1-M10 Leaches 1-4

Figure 12C: Potassium concentrations M1-M10 Leaches 1-4

56

Figure 13C: Magnesium concentrations M1-M10 Leaches 1-4

Figure 14C: Sodium concentrations M1-M10 Leaches 1-4

57

Figure 15C: Chloride concentrations M1-M10 Leaches 1-4

Figure 16C: Calcium concentrations M1-M10 Leaches 1-4

58

Appendix D

Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Spectrometry (EDXS)

Figure 1D: Cuttings sample leached in acid

from depth 8470 ft-8500 ft in the Utica

Formation showing a presence of barite

represented by the bright grains in the BSED

image.

Figure 2D: Cuttings sample leached in acid


Formation showing a large, euhedral barite

grain with smaller grains throughout the BSED

image.

Figure 3D: EDXS data confirming chemistry of cuttings sample leached in acid from depth

8470 ft-8500 ft in the Utica Formation where spot analysis was taken on the large, euhedral

grain presented in the BSED image.

59

Figure 4D: Cuttings sample leached in water


Formation showing barite grains throughout

the BSED image.

Figure 5D: Cuttings sample leached in water


Formation showing a large, euhedral barite

grain with smaller grains throughout the BSED

image.

Figure 6D: EDXS data confirming chemistry of cuttings sample leached in water from depth

8500 ft-8530 ft in the Utica Formation where spot analysis was taken on the large, euhedral

grain presented in the BSED image.

60

Figure 7D: Core sample leached in acid from

depth 8479 ft in the Point Pleasant Formation

showing dissolution textures throughout the

BSED image.

Figure 8D: EDXS data showing calcium carbonate chemistry of core sample leached in acid

from depth 8479 ft in the Point Pleasant Formation where spot analysis was taken on the

dissolution surface presented in the BSED image.

61

Figure 9D: Core sample leached in acid from

depth 8549 ft in the Point Pleasant Formation

showing pyrite framboids surrounded by illitic

clay throughout the BSED image.

Figure 10: EDXS data confirming pyrite presence in core sample leached in acid from depth

8549 ft in the Point Pleasant Formation where spot analysis was taken on the bright framboids


62

Appendix E

PHREEQC Geochemical Modeling

Table 1E: Input parameters for Leach 1




63

Phase: Saturation Index:

Aragonite -2.49

Calcite -2.35

Dolomite -5.81

Barite -2.02

Celestite -3.33

Gypsum -3.8

Strontianite -3.16

MW 1 Leach 1


Aragonite -1.14

Calcite -1

Dolomite -3.34

Barite -1.89

Celestite -3.29

Gypsum -3.26

Strontianite -2.31

MW 2 Leach 1


Aragonite -2.42

Calcite -2.27

Dolomite -5.69

Barite -2.43

Celestite -4.01

Gypsum -3.98

Strontianite -3.58

MW 3 Leach 1


Aragonite -1.18

Calcite -1.04

Dolomite -3.54

Barite -2.32

Celestite -3.85

Gypsum -3.44

Strontianite -2.74

MW 4 Leach 1


Aragonite -2.2

Calcite -2.06

Dolomite -5.18

Barite 0.09

Celestite -2.75

Gypsum -3.43

Strontianite -2.67

MW 5 Leach 1


Aragonite -2.17

Calcite -2.03

Dolomite -5.15

Barite 0.01

Celestite -2.9

Gypsum -3.51

Strontianite -2.71

MW 6 Leach 1

Table 5E: Saturation indices

MW1 Leach 1


MW2 Leach 1


MW3 Leach 1


MW4 Leach 1


MW5 Leach 1


MW6 Leach 1

64


Aragonite -2.27

Calcite -2.13

Dolomite -5.34

Barite -0.01

Celestite -2.98

Gypsum -3.63

Strontianite -2.77

MW 7 Leach 1


Aragonite -1.33

Calcite -1.18

Dolomite -3.54

Barite 0.01

Celestite -2.91

Gypsum -3.15

Strontianite -2.23

MW 8 Leach 1


Aragonite -1.15

Calcite -1

Dolomite -3.25

Barite -0.01

Celestite -2.95

Gypsum -3.09

Strontianite -2.15

MW 9 Leach 1


Aragonite -1.12

Calcite -0.97

Dolomite -3.16

Barite -0.03

Celestite -2.86

Gypsum -3.07

Strontianite -2.05

MW 10 Leach 1


Aragonite -2.44

Calcite -2.29

Dolomite -5.61

Barite -2.09

Celestite -3.28

Gypsum -3.95

Strontianite -2.9

MW 1 Leach 2


Aragonite -1.11

Calcite -0.97

Dolomite -3.27

Barite -1.67

Celestite -3.22

Gypsum -3.33

Strontianite -2.15

MW 2 Leach 2


MW7 Leach 1


MW8 Leach 1


MW9 Leach 1


MW10 Leach 1


MW1 Leach 2


MW2 Leach 2

65


Aragonite -2.45

Calcite -2.31

Dolomite -5.61

Barite -2.74

Celestite -4.43

Gypsum -4.33

Strontianite -3.7

MW 3 Leach 2


Aragonite -1.09

Calcite -0.94

Dolomite -3.32

Barite -2.75

Celestite -4.4

Gypsum -3.94

Strontianite -2.69

MW 4 Leach 2


Aragonite -2.19

Calcite -2.05

Dolomite -5.12

Barite -0.02

Celestite -2.97

Gypsum -3.68

Strontianite -2.62

MW 5 Leach 2


Aragonite -2.39

Calcite -2.25

Dolomite -5.6

Barite -0.13

Celestite -3.26

Gypsum -3.89

Strontianite -2.9

MW 6 Leach 2


Aragonite -2.38

Calcite -2.24

Dolomite -5.54

Barite -0.09

Celestite -3.25

Gypsum -3.89

Strontianite -2.88

MW 7 Leach 2


Aragonite -1.66

Calcite -1.52

Dolomite -4.1

Barite -0.02

Celestite -3.12

Gypsum -3.37

Strontianite -2.55

MW 8 Leach 2


MW3 Leach 2


MW4 Leach 2


MW5 Leach 2


MW6 Leach 2


MW7 Leach 2


MW8 Leach 2

66


Aragonite -1.26

Calcite -1.12

Dolomite -3.43

Barite -0.09

Celestite -3.17

Gypsum -3.31

Strontianite -2.26

MW 9 Leach 2


Aragonite -1.13

Calcite -0.99

Dolomite -3.17

Barite -0.11

Celestite -3.1

Gypsum -3.26

Strontianite -2.11

MW 10 Leach 2


Aragonite -2.15

Calcite -2

Dolomite -4.74

Barite -1.68

Celestite -2.98

Gypsum -3.77

Strontianite -2.5

MW 1 Leach 3


Aragonite -1.28

Calcite -1.14

Dolomite -3.46

Barite -1.4

Celestite -2.98

Gypsum -3.26

Strontianite -2.14

MW 2 Leach 3


Aragonite -2.08

Calcite -1.93

Dolomite -4.54

Barite -2.3

Celestite -4.22

Gypsum -4.13

Strontianite -3.3

MW 3 Leach 3


Aragonite -1.18

Calcite -1.04

Dolomite -3.28

Barite -2.33

Celestite -4.36

Gypsum -3.9

Strontianite -2.79

MW 4 Leach 3


MW9 Leach 2


MW10 Leach 2


MW1 Leach 3 Table 26E: Saturation indices

MW2 Leach 3



MW4 Leach 3

67


Aragonite -1.68

Calcite -1.54

Dolomite -3.77

Barite 0.03

Celestite -2.74

Gypsum -3.36

Strontianite -2.2

MW 5 Leach 3


Aragonite -1.89

Calcite -1.74

Dolomite -4.3

Barite -0.07

Celestite -2.99

Gypsum -3.5

Strontianite -2.52

MW 6 Leach 3


Aragonite -2.01

Calcite -1.87

Dolomite -4.49

Barite -0.02

Celestite -3.04

Gypsum -3.56

Strontianite -2.63

MW 7 Leach 3


Aragonite -1.3

Calcite -1.16

Dolomite -3.21

Barite 0

Celestite -3.08

Gypsum -3.19

Strontianite -2.34

MW 8 Leach 3


Aragonite -1.01

Calcite -0.87

Dolomite -2.78

Barite -0.09

Celestite -3.25

Gypsum -3.26

Strontianite -2.14

MW 9 Leach 3


Aragonite -0.96

Calcite -0.81

Dolomite -2.63

Barite 0

Celestite -3.15

Gypsum -3.12

Strontianite -2.12

MW 10 Leach 3


MW5 Leach 3


MW6 Leach 3


MW7 Leach 3


MW8 Leach 3



MW10 Leach 3

68


Aragonite -2.15

Calcite -2

Dolomite -4.74

Barite -1.99

Celestite -3.29

Gypsum -4.08

Strontianite -2.5

MW 1 Leach 4


Aragonite -1.29

Calcite -1.14

Dolomite -3.47

Barite -1.74

Celestite -3.32

Gypsum -3.61

Strontianite -2.14

MW 2 Leach 4


Aragonite -2.37

Calcite -2.22

Dolomite -5.04

Barite -2.1

Celestite -3.49

Gypsum -4.14

Strontianite -2.86

MW 3 Leach 4


Aragonite -0.9

Calcite -0.76

Dolomite -2.75

Barite -2.28

Celestite -4.02

Gypsum -3.97

Strontianite -2.1

MW 4 Leach 4


Aragonite -2.15

Calcite -2.1

Dolomite -4.55

Barite -2.1

Celestite -4.06

Gypsum -3.85

Strontianite -3.5

MW 5 Leach4


Aragonite -1.13

Calcite -0.98

Dolomite -3.16

Barite -1.76

Celestite -3.77

Gypsum -3.21

Strontianite -2.83

MW 6 Leach 4


MW1 Leach 4


MW2 Leach 4


MW3 Leach 4


MW4 Leach 4


MW5 Leach 4


MW6 Leach 4

69


Aragonite -1.49

Calcite -1.35

Dolomite -3.37

Barite -0.16

Celestite -3.34

Gypsum -3.67

Strontianite -2.3

MW 7 Leach 4


Aragonite -1.84

Calcite -1.7

Dolomite -4.17

Barite -0.25

Celestite -3.49

Gypsum -3.81

Strontianite -2.67

MW 8 Leach 4


Aragonite -2.01

Calcite -1.87

Dolomite -4.42

Barite -0.34

Celestite -3.71

Gypsum -4.04

Strontianite -2.82

MW 9 Leach 4


Aragonite -1.05

Calcite -0.91

Dolomite -2.78

Barite -0.17

Celestite -3.64

Gypsum -3.33

Strontianite -2.5

MW 10 Leach 4



MW8 Leach 4


MW9 Leach 4


MW10 Leach 4

Documents

Potential Sources of Salts from Water-Rock Interaction